Patent GB-679950-A (GB)
Title: Improvements in or relating to apparatus for use in serial radiography
IPC: G03B42/02
Filed: 1950-06-16
Abstract: 679,950. X-ray apparatus. GENERAL ELECTRIC CO., Ltd., and BRYER, R. F. May 31, 1951 [June 16, 1950], No. 1609,9/50. Class 98 (i). Apparatus for use in serial radiography comprises in combination a film cassette holder, a frame which supports the cassette holder so that it may be moved along a predetermined track, and a number of stops mounted on the frame at different positions along the track, each stop being spring loaded so that it normally occupies one of two positions, in the first of which the stop is disposed so as to engage the cassette holder if it is moved up to the stop in a given direction (which is the same for all stops) along the track, and in the second of which the stop is disposed so as not to. engage with the cassette holder when it is moved in either direction along the track, the arrangement being such that the engagement of a stop with the cassette holder serves to locate the cassette holder in a desired position along the track and also moves the stop into an intermediate position from which it will move automatically to the second extreme position if the cassette holder is moved a short distance along the track in a direction opposite to the given direction. As shown, an X-ray cassette holder 1 is slidable in channels 3, 4 mounted in a frame 2. Slots 7, 8, 9 are formed in channel 4, and adjacent to each slot a plate 10 is mounted by a pivot 13 at one corner thereof. Plate 10 has a circular aperture 12 into which extends a projection 14 mounted on the frame 2. The plate can thus pivot between an upper position shown at the left, in which it is clear of the path of the cassette holder, and a lower position shown at the right, in which it extends through the slot in channel 4 into the path of the cassette. The plate is normally urged into one position or the other by a spring 17 coiled around a rod 15, one end of which is pivoted to plate 10, and the other end of which slides in a pin 16, pivoted in the frame 2. Initially, the cassette holder is drawn to the left and the plates 10 are all brought to the upper position by actuating a lever 21 pivoted to the frame 2. This lever moves a rod 18, consisting of two strips spaced apart longitudinally by bolts 19, so that bolts 19 press plates 10 upward. Each plate 10 has a slot 11 formed at one side, the slot having one side sloping inward from the corner where pivot 13 is located. As the cassette holder approaches the first plate 10, a flange 6 on the holder enters slot 11, so that the cassette is held in a first position and plate 10 is rocked into an intermediate position, as shown in the centre. When the holder is drawn back, spring 17 pushes plate 10 into its lower position, so that the holder can move over the plate until it is stopped by the second plate, after which it is drawn back and moved until stopped by the third plate, then moved back again and moved to the end of channels 3, 4. In each of the last three positions, a third of the cassette surface is exposed, for making a radiograph, through an aperture in a lead screen (not shown). Lever 21 has a projection 22 which extends into the path of the cassette holder until the lever is rocked, so that when the radiographs have been made, the cassette holder cannot be withdrawn from the frame 2 until the plates 10 have been returned to their upper positions. A modified construction of plate 10, which acts in a similar manner, is also described.